Method and apparatus for intensity control of a charged particle beam extracted from a synchrotron

ABSTRACT

The invention comprises intensity control of a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors. Particularly, intensity of a charged particle stream of a synchrotron is described. Intensity control is described in combination with turning magnets, edge focusing magnets, concentrating magnetic field magnets, winding and control coils, and extraction elements of the synchrotron. The system reduces the overall size of the synchrotron, provides a tightly controlled proton beam, directly reduces the size of required magnetic fields, directly reduces required operating power, and allows continual acceleration of protons in a synchrotron even during a process of extracting protons from the synchrotron.

CROSS REFERENCES TO RELATED APPLICATIONS

This application:

-   -   is a continuation-in-part of U.S. patent application Ser. No.        12/425,683 filed Apr. 17, 2009, which claims the benefit of:        -   U.S. provisional patent application No. 61/055,395 filed May            22, 2008;        -   U.S. provisional patent application No. 61/137,574 filed            Aug. 1, 2008;        -   U.S. provisional patent application No. 61/192,245 filed            Sep. 17, 2008;        -   U.S. provisional patent application No. 61/055,409 filed May            22, 2008;        -   U.S. provisional patent application No. 61/203,308 filed            Dec. 22, 2008;        -   U.S. provisional patent application No. 61/188,407 filed            Aug. 11, 2008;        -   U.S. provisional patent application No. 61/188,406 filed            Aug. 11, 2008;        -   U.S. provisional patent application No. 61/189,815 filed            Aug. 25, 2008;        -   U.S. provisional patent application No. 61/201,731 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/205,362 filed            Jan. 21, 2009;        -   U.S. provisional patent application No. 61/134,717 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/134,707 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/201,732 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/198,509 filed            Nov. 7, 2008;        -   U.S. provisional patent application No. 61/134,718 filed            Jul. 14, 2008;        -   U.S. provisional patent application No. 61/190,613 filed            Sep. 2, 2008;        -   U.S. provisional patent application No. 61/191,043 filed            Sep. 8, 2008;        -   U.S. provisional patent application No. 61/192,237 filed            Sep. 17, 2008;        -   U.S. provisional patent application No. 61/201,728 filed            Dec. 15, 2008;        -   U.S. provisional patent application No. 61/190,546 filed            Sep. 2, 2008;        -   U.S. provisional patent application No. 61/189,017 filed            Aug. 15, 2008;        -   U.S. provisional patent application No. 61/198,248 filed            Nov. 5, 2008;        -   U.S. provisional patent application No. 61/198,508 filed            Nov. 7, 2008;        -   U.S. provisional patent application No. 61/197,971 filed            Nov. 3, 2008;        -   U.S. provisional patent application No. 61/199,405 filed            Nov. 17, 2008;        -   U.S. provisional patent application No. 61/199,403 filed            Nov. 17, 2008; and        -   U.S. provisional patent application No. 61/199,404 filed            Nov. 17, 2008;    -   claims the benefit of U.S. provisional patent application No.        61/209,529 filed Mar. 9, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/208,182 filed Feb. 23, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/208,971 filed Mar. 3, 2009;    -   claims the benefit of U.S. provisional patent application No.        61/270,298 filed Jul. 7, 2009; and    -   claims priority to PCT patent application serial No.:        PCT/RU2009/00015, filed Mar. 4, 2009,    -   all of which are incorporated herein in their entirety by this        reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to treatment of solid cancers. Moreparticularly, the invention relates to magnetic field control elementsused in conjunction with charged particle cancer therapy beamacceleration, extraction, and/or targeting methods and apparatus.

2. Discussion of the Prior Art

Cancer

A tumor is an abnormal mass of tissue. Tumors are either benign ormalignant. A benign tumor grows locally, but does not spread to otherparts of the body. Benign tumors cause problems because of their spread,as they press and displace normal tissues. Benign tumors are dangerousin confined places such as the skull. A malignant tumor is capable ofinvading other regions of the body. Metastasis is cancer spreading byinvading normal tissue and spreading to distant tissues.

Cancer Treatment

Several forms of radiation therapy exist for cancer treatment including:brachytherapy, traditional electromagnetic X-ray therapy, and protontherapy. Each are further described, infra.

Brachytherapy is radiation therapy using radioactive sources implantedinside the body. In this treatment, an oncologist implants radioactivematerial directly into the tumor or very close to it. Radioactivesources are also placed within body cavities, such as the uterinecervix.

The second form of traditional cancer treatment using electromagneticradiation includes treatment using X-rays and gamma rays. An X-ray ishigh-energy, ionizing, electromagnetic radiation that is used at lowdoses to diagnose disease or at high doses to treat cancer. An X-ray orRöntgen ray is a form of electromagnetic radiation with a wavelength inthe range of 10 to 0.01 nanometers (nm), corresponding to frequencies inthe range of 30 PHz to 30 EHz. X-rays are longer than gamma rays andshorter than ultraviolet rays. X-rays are primarily used for diagnosticradiography. X-rays are a form of ionizing radiation and as such can bedangerous. Gamma rays are also a form of electromagnetic radiation andare at frequencies produced by sub-atomic particle interactions, such aselectron-positron annihilation or radioactive decay. In theelectromagnetic spectrum, gamma rays are generally characterized aselectromagnetic radiation having the highest frequency, as havinghighest energy, and having the shortest wavelength, such as below about10 picometers. Gamma rays consist of high energy photons with energiesabove about 100 keV. X-rays are commonly used to treat cancerous tumors.However, X-rays are not optimal for treatment of cancerous tissue asX-rays deposit their highest does of radiation near the surface of thetargeted tissue and delivery exponentially less radiation as theypenetrate into the tissue. This results in large amounts of radiationbeing delivered outside of the tumor. Gamma rays have similarlimitations.

The third form of cancer treatment uses protons. Proton therapy systemstypically include: a beam generator, an accelerator, and a beamtransport system to move the resulting accelerated protons to aplurality of treatment rooms where the protons are delivered to a tumorin a patient's body.

Proton therapy works by aiming energetic ionizing particles, such asprotons accelerated with a particle accelerator, onto a target tumor.These particles damage the DNA of cells, ultimately causing their death.Cancerous cells, because of their high rate of division and theirreduced ability to repair damaged DNA, are particularly vulnerable toattack on their DNA.

Due to their relatively enormous size, protons scatter less easily inthe tissue and there is very little lateral dispersion. Hence, theproton beam stays focused on the tumor shape without much lateral damageto surrounding tissue. All protons of a given energy have a certainrange, defined by the Bragg peak, and the dosage delivery to tissueratio is maximum over just the last few millimeters of the particle'srange. The penetration depth depends on the energy of the particles,which is directly related to the speed to which the particles wereaccelerated by the proton accelerator. The speed of the proton isadjustable to the maximum rating of the accelerator. It is thereforepossible to focus the cell damage due to the proton beam at the verydepth in the tissues where the tumor is situated. Tissues situatedbefore the Bragg peak receive some reduced dose and tissues situatedafter the peak receive none.

Synchrotrons

Patents related to the current invention are summarized here.

Proton Beam Therapy System

F. Cole, et. al. of Loma Linda University Medical Center “Multi-StationProton Beam Therapy System”, U.S. Pat. No. 4,870,287 (Sep. 26, 1989)describe a proton beam therapy system for selectively generating andtransporting proton beams from a single proton source and accelerator toa selected treatment room of a plurality of patient treatment rooms.

Injection

K. Hiramoto, et. al. “Accelerator System”, U.S. Pat. No. 4,870,287 (Sep.26, 1989) describes an accelerator system having a selectorelectromagnet for introducing an ion beam accelerated bypre-accelerators into either a radioisotope producing unit or asynchrotron.

K. Hiramoto, et. al. “Circular Accelerator, Method of Injection ofCharged Particle Thereof, and Apparatus for Injection of ChargedParticle Thereof”, U.S. Pat. No. 5,789,875 (Aug. 4, 1998) and K.Hiramoto, et. al. “Circular Accelerator, Method of Injection of ChargedParticle Thereof, and Apparatus for Injection of Charged ParticleThereof”, U.S. Pat. No. 5,600,213 (Feb. 4, 1997) both describe a methodand apparatus for injecting a large number of charged particles into avacuum duct where the beam of injection has a height and width relativeto a geometrical center of the duct.

Accelerator/Synchrotron

H. Tanaka, et. al. “Charged Particle Accelerator”, U.S. Pat. No.7,259,529 (Aug. 21, 2007) describe a charged particle accelerator havinga two period acceleration process with a fixed magnetic field applied inthe first period and a timed second acceleration period to providecompact and high power acceleration of the charged particles.

T. Haberer, et. al. “Ion Beam Therapy System and a Method for Operatingthe System”, U.S. Pat. No. 6,683,318 (Jan. 27, 2004) describe an ionbeam therapy system and method for operating the system. The ion beamsystem uses a gantry that has vertical deflection system and ahorizontal deflection system positioned before a last bending magnetthat result in a parallel scanning mode resulting from an edge focusingeffect.

V. Kulish, et. al. “Inductional Undulative EH-Accelerator”, U.S. Pat.No. 6,433,494 (Aug. 13, 2002) describe an inductive undulativeEH-accelerator for acceleration of beams of charged particles. Thedevice consists of an electromagnet undulation system, whose drivingsystem for electromagnets is made in the form of a radio-frequency (RF)oscillator operating in the frequency range from about 100 KHz to 10GHz.

K. Saito, et. al. “Radio-Frequency Accelerating System and Ring TypeAccelerator Provided with the Same”, U.S. Pat. No. 5,917,293 (Jun. 29,1999) describe a radio-frequency accelerating system having a loopantenna coupled to a magnetic core group and impedance adjusting meansconnected to the loop antenna. A relatively low voltage is applied tothe impedance adjusting means allowing small construction of theadjusting means.

J. Hirota, et. al. “Ion Beam Accelerating Device Having SeparatelyExcited Magnetic Cores”, U.S. Pat. No. 5,661,366 (Aug. 26, 1997)describe an ion beam accelerating device having a plurality of highfrequency magnetic field inducing units and magnetic cores.

J. Hirota, et. al. “Acceleration Device for Charged Particles”, U.S.Pat. No. 5,168,241 (Dec. 1, 1992) describe an acceleration cavity havinga high frequency power source and a looped conductor operating under acontrol that combine to control a coupling constant and/or de-tuningallowing transmission of power more efficiently to the particles.

Vacuum Chamber

T. Kobari, et. al. “Apparatus For Treating the Inner Surface of VacuumChamber”, U.S. Pat. No. 5,820,320 (Oct. 13, 1998) and T. Kobari, et. al.“Process and Apparatus for Treating Inner Surface Treatment of Chamberand Vacuum Chamber”, U.S. Pat. No. 5,626,682 (May 6, 1997) both describean apparatus for treating an inner surface of a vacuum chamber includingmeans for supplying an inert gas or nitrogen to a surface of the vacuumchamber with a broach. Alternatively, the broach is used for supplying alower alcohol to the vacuum chamber for dissolving contaminants on thesurface of the vacuum chamber.

Magnet Shape

M. Tadokoro, et. al. “Electromagnetic and Magnetic Field GeneratingApparatus”, U.S. Pat. No. 6,365,894 (Apr. 2, 2002) and M. Tadokoro, et.al. “Electromagnetic and Magnetic Field Generating Apparatus”, U.S. Pat.No. 6,236,043 (May 22, 2001) each describe a pair of magnetic poles, areturn yoke, and exciting coils. The interior of the magnetic poles eachhave a plurality of air gap spacers to increase magnetic field strength.

Extraction

T. Nakanishi, et. al. “Charged-Particle Beam Accelerator, Particle BeamRadiation Therapy System Using the Charged-Particle Beam Accelerator,and Method of Operating the Particle Beam Radiation Therapy System”,U.S. Pat. No. 7,122,978 (Oct. 17, 2006) describe a charged particle beamaccelerator having an RF-KO unit for increasing amplitude of betatronoscillation of a charged particle beam within a stable region ofresonance and an extraction quadrupole electromagnet unit for varying astable region of resonance. The RF-KO unit is operated within afrequency range in which the circulating beam does not go beyond aboundary of stable region of resonance and the extraction quadrupoleelectromagnet is operated with timing required for beam extraction.

T. Haberer, et. al. “Method and Device for Controlling a Beam ExtractionRaster Scan Irradiation Device for Heavy Ions or Protons”, U.S. Pat. No.7,091,478 (Aug. 15, 2006) describe a method for controlling beamextraction irradiation in terms of beam energy, beam focusing, and beamintensity for every accelerator cycle.

K. Hiramoto, et. al. “Accelerator and Medical System and OperatingMethod of the Same”, U.S. Pat. No. 6,472,834 (Oct. 29, 2002) describe acyclic type accelerator having a deflection electromagnet and four-poleelectromagnets for making a charged particle beam circulate, amulti-pole electromagnet for generating a stability limit of resonanceof betatron oscillation, and a high frequency source for applying a highfrequency electromagnetic field to the beam to move the beam to theoutside of the stability limit. The high frequency source generates asum signal of a plurality of alternating current (AC) signals of whichthe instantaneous frequencies change with respect to time, and of whichthe average values of the instantaneous frequencies with respect to timeare different. The system applies the sum signal via electrodes to thebeam.

K. Hiramoto, et. al. “Synchrotron Type Accelerator and Medical TreatmentSystem Employing the Same”, U.S. Pat. No. 6,087,670 (Jul. 11, 2000) andK. Hiramoto, et. al. “Synchrotron Type Accelerator and Medical TreatmentSystem Employing the Same”, U.S. Pat. No. 6,008,499 (Dec. 28, 1999)describe a synchrotron accelerator having a high frequency applying unitarranged on a circulating orbit for applying a high frequencyelectromagnetic field to a charged particle beam circulating and forincreasing amplitude of betatron oscillation of the particle beam to alevel above a stability limit of resonance. Additionally, for beamejection, four-pole divergence electromagnets are arranged: (1)downstream with respect to a first deflector; (2) upstream with respectto a deflecting electromagnet; (3) downstream with respect to thedeflecting electromagnet; and (4) and upstream with respect to a seconddeflector.

K. Hiramoto, et. al. “Circular Accelerator and Method and Apparatus forExtracting Charged-Particle Beam in Circular Accelerator”, U.S. Pat. No.5,363,008 (Nov. 8, 1994) describe a circular accelerator for extractinga charged-particle beam that is arranged to: (1) increase displacementof a beam by the effect of betatron oscillation resonance; (2) toincrease the betatron oscillation amplitude of the particles, which havean initial betatron oscillation within a stability limit for resonance;and (3) to exceed the resonance stability limit thereby extracting theparticles exceeding the stability limit of the resonance.

K. Hiramoto, et. al. “Method of Extracting Charged Particles fromAccelerator, and Accelerator Capable Carrying Out the Method, byShifting Particle Orbit”, U.S. Pat. No. 5,285,166 (Feb. 8, 1994)describe a method of extracting a charged particle beam. An equilibriumorbit of charged particles maintained by a bending magnet and magnetshaving multipole components greater than sextuple components is shiftedby a constituent element of the accelerator other than these magnets tochange the tune of the charged particles.

Transport/Scanning Control

K. Matsuda, et. al. “Particle Beam Irradiation Apparatus, TreatmentPlanning Unit, and Particle Beam Irradiation Method”, U.S. Pat. No.7,227,161 (Jun. 5, 2007); K. Matsuda, et. al. “Particle Beam IrradiationTreatment Planning Unit, and Particle Beam Irradiation Method”, U.S.Pat. No. 7,122,811 (Oct. 17, 2006); and K. Matsuda, et. al. “ParticleBeam Irradiation Apparatus, Treatment Planning Unit, and Particle BeamIrradiation Method” (Sep. 5, 2006) describe a particle beam irradiationapparatus have a scanning controller that stops output of an ion beam,changes irradiation position via control of scanning electromagnets, andreinitiates treatment based on treatment planning information.

T. Norimine, et. al. “Particle Therapy System Apparatus”, U.S. Pat. No.7,060,997 (Jun. 13, 2006); T. Norimine, et. al. “Particle Therapy SystemApparatus”, U.S. Pat. No. 6,936,832 (Aug. 30, 2005); and T. Norimine,et. al. “Particle Therapy System Apparatus”, U.S. Pat. No. 6,774,383(Aug. 10, 2004) each describe a particle therapy system having a firststeering magnet and a second steering magnet disposed in a chargedparticle beam path after a synchrotron that are controlled by first andsecond beam position monitors.

K. Moriyama, et. al. “Particle Beam Therapy System”, U.S. Pat. No.7,012,267 (Mar. 14, 2006) describe a manual input to a ready signalindicating preparations are completed for transport of the ion beam to apatient.

H. Harada, et. al. “Irradiation Apparatus and Irradiation Method”, U.S.Pat. No. 6,984,835 (Jan. 10, 2006) describe an irradiation method havinga large irradiation filed capable of uniform dose distribution, withoutstrengthening performance of an irradiation field device, using aposition controller having overlapping area formed by a plurality ofirradiations using a multileaf collimator. The system provides flat anduniform dose distribution over an entire surface of a target.

H. Akiyama, et. al. “Charged Particle Beam Irradiation Equipment HavingScanning Electromagnet Power Supplies”, U.S. Pat. No. 6,903,351 (Jun. 7,2005); H. Akiyama, et. al. “Charged Particle Beam Irradiation EquipmentHaving Scanning Electromagnet Power Supplies”, U.S. Pat. No. 6,900,436(May 31, 2005); and H. Akiyama, et. al. “Charged Particle BeamIrradiation Equipment Having Scanning Electromagnet Power Supplies”,U.S. Pat. No. 6,881,970 (Apr. 19, 2005) all describe a power supply forapplying a voltage to a scanning electromagnet for deflecting a chargedparticle beam and a second power supply without a pulsating component tocontrol the scanning electromagnet more precisely allowing for uniformirradiation of the irradiation object.

K. Amemiya, et. al. “Accelerator System and Medical AcceleratorFacility”, U.S. Pat. No. 6,800,866 (Oct. 5, 2004) describe anaccelerator system having a wide ion beam control current range capableof operating with low power consumption and having a long maintenanceinterval.

A. Dolinskii, et. al. “Gantry with an Ion-Optical System”, U.S. Pat. No.6,476,403 (Nov. 5, 2002) describe a gantry for an ion-optical systemcomprising an ion source and three bending magnets for deflecting an ionbeam about an axis of rotation. A plurality of quadrupoles are alsoprovided along the beam path to create a fully achromatic beam transportand an ion beam with difference emittances in the horizontal andvertical planes. Further, two scanning magnets are provided between thesecond and third bending magnets to direct the beam.

H. Akiyama, et. al. “Charged Particle Beam Irradiation Apparatus”, U.S.Pat. No. 6,218,675 (Apr. 17, 2001) describe a charged particle beamirradiation apparatus for irradiating a target with a charged particlebeam that include a plurality of scanning electromagnets and aquadrupole electromagnet between two of the plurality of scanningelectromagnets.

K. Matsuda, et. al. “Charged Particle Beam Irradiation System and MethodThereof”, U.S. Pat. No. 6,087,672 (Jul. 11, 2000) describe a chargedparticle beam irradiation system having a ridge filter with shieldingelements to shield a part of the charged particle beam in an areacorresponding to a thin region in said target.

P. Young, et. al. “Raster Scan Control System for a Charged-ParticleBeam”, U.S. Pat. No. 5,017,789 (May 21, 1991) describe a raster scancontrol system for use with a charged-particle beam delivery system thatincludes a nozzle through which a charged particle beam passes. Thenozzle includes a programmable raster generator and both fast and slowsweep scan electromagnets that cooperate to generate a sweeping magneticfield that steers the beam along a desired raster scan pattern at atarget.

Beam Shape Control

M. Yanagisawa, et. al. “Particle Beam Irradiation System and Method ofAdjusting Irradiation Field Forming Apparatus”, U.S. Pat. No. 7,154,107(Dec. 26, 2006) and M. Yanagisawa, et. al. “Particle Beam IrradiationSystem and Method of Adjusting Irradiation Field Forming Apparatus”,U.S. Pat. No. 7,049,613 (May 23, 2006) describe a particle therapysystem having a scattering compensator and a range modulation wheel.Movement of the scattering compensator and the range modulation wheeladjusts a size of the ion beam and scattering intensity resulting inpenumbra control and a more uniform dose distribution to a diseased bodypart.

T. Haberer, et. al. “Device and Method for Adapting the Size of an IonBeam Spot in the Domain of Tumor Irradiation”, U.S. Pat. No. 6,859,741(Feb. 22, 2005) describe a method and apparatus for adapting the size ofan ion beam in tumor irradiation. Quadrupole magnets determining thesize of the ion beam spot are arranged directly in front of rasterscanning magnets determining the size of the ion beam spot. Theapparatus contains a control loop for obtaining current correctionvalues to further control the ion beam spot size.

K. Matsuda, et. al. “Charged Particle Irradiation Apparatus and anOperating Method Thereof”, U.S. Pat. No. 5,986,274 (Nov. 16, 1999)describe a charged particle irradiation apparatus capable of decreasinga lateral dose falloff at boundaries of an irradiation field of acharged particle beam using controlling magnet fields of quadrupoleelectromagnets and deflection electromagnets to control the center ofthe charged particle beam passing through the center of a scattererirrespective of direction and intensity of a magnetic field generated byscanning electromagnets.

K. Hiramoto, et. al. “Charged Particle Beam Apparatus and Method forOperating the Same”, U.S. Pat. No. 5,969,367 (Oct. 19, 1999) describe acharged particle beam apparatus where a the charged particle beam isenlarged by a scatterer resulting in a Gaussian distribution that allowsoverlapping of irradiation doses applied to varying spot positions.

M. Moyers, et. al. “Charged Particle Beam Scattering System”, U.S. Pat.No. 5,440,133 (Aug. 8, 1995) describe a radiation treatment apparatusfor producing a particle beam and a scattering foil for changing thediameter of the charged particle beam.

C. Nunan “Multileaf Collimator for Radiotherapy Machines”, U.S. Pat. No.4,868,844 (Sep. 19,1989) describes a radiation therapy machine having amultileaf collimator formed of a plurality of heavy metal leaf barsmovable to form a rectangular irradiation field.

R. Maughan, et. al. “Variable Radiation Collimator”, U.S. Pat. No.4,754,147 (Jun. 28, 1988) describe a variable collimator for shaping across-section of a radiation beam that relies on rods, which arepositioned around a beam axis. The rods are shaped by a shaping membercut to a shape of an area of a patient go be irradiated.

Beam Energy/Intensity

M. Yanagisawa, et. al. “Charged Particle Therapy System, RangeModulation Wheel Device, and Method of Installing Range Modulation WheelDevice”, U.S. Pat. No. 7,355,189 (Apr. 8, 2008) and Yanagisawa, et. al.“Charged Particle Therapy System, Range Modulation Wheel Device, andMethod of Installing Range Modulation Wheel Device”, U.S. Pat. No.7,053,389 (May 30, 2008) both describe a particle therapy system havinga range modulation wheel. The ion beam passes through the rangemodulation wheel resulting in a plurality of energy levels correspondingto a plurality of stepped thicknesses of the range modulation wheel.

M. Yanagisawa, et. al. “Particle Beam Irradiation System and Method ofAdjusting Irradiation Apparatus”, U.S. Pat. No. 7,297,967 (Nov. 20,2007); M. Yanagisawa, et. al. “Particle Beam Irradiation System andMethod of Adjusting Irradiation Apparatus”, U.S. Pat. No. 7,071,479(Jul. 4, 2006); M. Yanagisawa, et. al. “Particle Beam Irradiation Systemand Method of Adjusting Irradiation Apparatus”, U.S. Pat. No. 7,026,636(Apr. 11, 2006); and M. Yanagisawa, et. al. “Particle Beam IrradiationSystem and Method of Adjusting Irradiation Apparatus”, U.S. Pat. No.6,777,700 (Aug. 17, 2004) all describe a scattering device, a rangeadjustment device, and a peak spreading device. The scattering deviceand range adjustment device are combined together and are moved along abeam axis. The spreading device is independently moved along the axis toadjust the degree of ion beam scattering. Combined, the devise increasesthe degree of uniformity of radiation dose distribution to a diseasedtissue.

A. Sliski, et. al. “Programmable Particle Scatterer for RadiationTherapy Beam Formation”, U.S. Pat. No. 7,208,748 (Apr. 24, 2007)describe a programmable pathlength of a fluid disposed into a particlebeam to modulate scattering angle and beam range in a predeterminedmanner. The charged particle beam scatterer/range modulator comprises afluid reservoir having opposing walls in a particle beam path and adrive to adjust the distance between the walls of the fluid reservoirunder control of a programmable controller to create a predeterminedspread out Bragg peak at a predetermined depth in a tissue. The beamscattering and modulation is continuously and dynamically adjustedduring treatment of a tumor to deposit a dose in a targetedpredetermined three dimensional volume.

M. Tadokoro, et. al. “Particle Therapy System”, U.S. Pat. No. 7,247,869(Jul. 24, 2007) and U.S. Pat. No. 7,154,108 (Dec. 26, 2006) eachdescribe a particle therapy system capable of measuring energy of acharged particle beam during irradiation during use. The system includesa beam passage between a pair of collimators, an energy detectormounted, and a signal processing unit.

G. Kraft, et. al. “Ion Beam Scanner System and Operating Method”, U.S.Pat. No. 6,891,177 (May 10, 2005) describe an ion beam scanning systemhaving a mechanical alignment system for the target volume to be scannedand allowing for depth modulation of the ion beam by means of a linearmotor and transverse displacement of energy absorption means resultingin depth-staggered scanning of volume elements of a target volume.

G. Hartmann, et. al. “Method for Operating an Ion Beam Therapy System byMonitoring the Distribution of the Radiation Dose”, U.S. Pat. No.6,736,831 (May 18, 2004) describe a method for operation of an ion beamtherapy system having a grid scanner and irradiates and scans an areasurrounding an isocentre. Both the depth dose distribution and thetransverse dose distribution of the grid scanner device at variouspositions in the region of the isocentre are measured and evaluated.

Y. Jongen “Method for Treating a Target Volume with a Particle Beam andDevice Implementing Same”, U.S. Pat. No. 6,717,162 (Apr. 6, 2004)describes a method of producing from a particle beam a narrow spotdirected towards a target volume, characterized in that the spotsweeping speed and particle beam intensity are simultaneously varied.

G. Kraft, et. al. “Device for Irradiating a Tumor Tissue”, U.S. Pat. No.6,710,362 (Mar. 23, 2004) describe a method and apparatus of irradiatinga tumor tissue, where the apparatus has an electromagnetically drivenion-braking device in the proton beam path for depth-wise adaptation ofthe proton beam that adjusts both the ion beam direction and ion beamrange.

K. Matsuda, et. al. “Charged Particle Beam Irradiation Apparatus”, U.S.Pat. No. 6,617,598 (Sep. 9, 2003) describe a charged particle beamirradiation apparatus that increased the width in a depth direction of aBragg peak by passing the Bragg peak through an enlarging devicecontaining three ion beam components having different energies producedaccording to the difference between passed positions of each of thefilter elements.

H. Stelzer, et. al. “Ionization Chamber for Ion Beams and Method forMonitoring the Intensity of an Ion Beam”, U.S. Pat. No. 6,437,513 (Aug.20, 2002) describe an ionization chamber for ion beams and a method ofmonitoring the intensity of an ion therapy beam. The ionization chamberincludes a chamber housing, a beam inlet window, a beam outlet window, abeam outlet window, and a chamber volume filled with counting gas.

H. Akiyama, et. al. “Charged-Particle Beam Irradiation Method andSystem”, U.S. Pat. No. 6,433,349 (Aug. 13, 2002) and H. Akiyama, et. al.“Charged-Particle Beam Irradiation Method and System”, U.S. Pat. No.6,265,837 (Jul. 24, 2001) both describe a charged particle beamirradiation system that includes a changer for changing energy of theparticle and an intensity controller for controlling an intensity of thecharged-particle beam.

Y. Pu “Charged Particle Beam Irradiation Apparatus and Method ofIrradiation with Charged Particle Beam”, U.S. Pat. No. 6,034,377 (Mar.7, 2000) describes a charged particle beam irradiation apparatus havingan energy degrader comprising: (1) a cylindrical member having a length;and (2) a distribution of wall thickness in a circumferential directionaround an axis of rotation, where thickness of the wall determinesenergy degradation of the irradiation beam.

Dosage

K. Matsuda, et. al. “Particle Beam Irradiation System”, U.S. Pat. No.7,372,053 (Nov. 27, 2007) describe a particle beam irradiation systemensuring a more uniform dose distribution at an irradiation objectthrough use of a stop signal, which stops the output of the ion beamfrom the irradiation device.

H. Sakamoto, et. al. “Radiation Treatment Plan Making System andMethod”, U.S. Pat. No. 7,054,801 (May 30, 2006) describe a radiationexposure system that divides an exposure region into a plurality ofexposure regions and uses a radiation simulation to plan radiationtreatment conditions to obtain flat radiation exposure to the desiredregion.

G. Hartmann, et. al. “Method For Verifying the Calculated Radiation Doseof an Ion Beam Therapy System”, U.S. Pat. No. 6,799,068 (Sep. 28, 2004)describe a method for the verification of the calculated dose of an ionbeam therapy system that comprises a phantom and a discrepancy betweenthe calculated radiation dose and the phantom.

H. Brand, et. al. “Method for Monitoring the Irradiation Control of anIon Beam Therapy System”, U.S. Pat. No. 6,614,038 (Sep. 2, 2003)describe a method of checking a calculated irradiation control unit ofan ion beam therapy system, where scan data sets, control computerparameters, measuring sensor parameters, and desired current values ofscanner magnets are permanently stored.

T. Kan, et. al. “Water Phantom Type Dose Distribution DeterminingApparatus”, U.S. Pat. No. 6,207,952 (Mar. 27, 2001) describe a waterphantom type dose distribution apparatus that includes a closed watertank, filled with water to the brim, having an inserted sensor that isused to determine an actual dose distribution of radiation prior toradiation therapy.

Starting/Stopping Irradiation

K. Hiramoto, et. al. “Charged Particle Beam Apparatus and Method forOperating the Same”, U.S. Pat. No. 6,316,776 (Nov. 13, 2001) describe acharged particle beam apparatus where a charged particle beam ispositioned, started, stopped, and repositioned repetitively. Residualparticles are used in the accelerator without supplying new particles ifsufficient charge is available.

K. Matsuda, et. al. “Method and Apparatus for Controlling CircularAccelerator”, U.S. Pat. No. 6,462,490 (Oct. 8, 2002) describe a controlmethod and apparatus for a circular accelerator for adjusting timing ofemitted charged particles. The clock pulse is suspended after deliveryof a charged particle stream and is resumed on the basis of state of anobject to be irradiated.

Movable Patient

N. Rigney, et. al. “Patient Alignment System with External Measurementand Object Coordination for Radiation Therapy System”, U.S. Pat. No.7,199,382 (Apr. 3, 2007) describe a patient alignment system for aradiation therapy system that includes multiple external measurementdevices that obtain position measurements of movable components of theradiation therapy system. The alignment system uses the externalmeasurements to provide corrective positioning feedback to moreprecisely register the patient to the radiation beam.

Y. Muramatsu, et. al. “Medical Particle Irradiation Apparatus”, U.S.Pat. No. 7,030,396 (Apr. 18, 2006); Y. Muramatsu, et. al. “MedicalParticle Irradiation Apparatus”, U.S. Pat. No. 6,903,356 (Jun. 7, 2005);and Y. Muramatsu, et. al. “Medical Particle Irradiation Apparatus”, U.S.Pat. No. 6,803,591 (Oct. 12, 2004) all describe a medical particleirradiation apparatus having a rotating gantry, an annular frame locatedwithin the gantry such that is can rotate relative to the rotatinggantry, an anti-correlation mechanism to keep the frame from rotatingwith the gantry, and a flexible moving floor engaged with the frame issuch a manner to move freely with a substantially level bottom while thegantry rotates.

H. Nonaka, et. al. “Rotating Radiation Chamber for Radiation Therapy”,U.S. Pat. No. 5,993,373 (Nov. 30, 1999) describe a horizontal movablefloor composed of a series of multiple plates that are connected in afree and flexible manner, where the movable floor is moved in synchronywith rotation of a radiation beam irradiation section.

Respiration

K. Matsuda “Radioactive Beam Irradiation Method and Apparatus TakingMovement of the Irradiation Area Into Consideration”, U.S. Pat. No.5,538,494 (Jul. 23, 1996) describes a method and apparatus that enablesirradiation even in the case of a diseased part changing position due tophysical activity, such as breathing and heart beat. Initially, aposition change of a diseased body part and physical activity of thepatient are measured concurrently and a relationship therebetween isdefined as a function. Radiation therapy is performed in accordance tothe function.

Patient Positioning

Y. Nagamine, et. al. “Patient Positioning Device and Patient PositioningMethod”, U.S. Pat. Nos. 7,212,609 and 7,212,608 (May 1, 2007) describe apatient positioning system that compares a comparison area of areference X-ray image and a current X-ray image of a current patientlocation using pattern matching.

D. Miller, et. al. “Modular Patient Support System”, U.S. Pat. No.7,173,265 (Feb. 6, 2007) describe a radiation treatment system having apatient support system that includes a modularly expandable patient podand at least one immobilization device, such as a moldable foam cradle.

K. Kato, et. al. “Multi-Leaf Collimator and Medical System IncludingAccelerator”, U.S. Pat. No. 6,931,100 (Aug. 16, 2005); K. Kato, et. al.“Multi-Leaf Collimator and Medical System Including Accelerator”, U.S.Pat. No. 6,823,045 (Nov. 23, 2004); K. Kato, et. al. “Multi-LeafCollimator and Medical System Including Accelerator”, U.S. Pat. No.6,819,743 (Nov. 16, 2004); and K. Kato, et. al. “Multi-Leaf Collimatorand Medical System Including Accelerator”, U.S. Pat. No. 6,792,078 (Sep.14, 2004) all describe a system of leaf plates used to shortenpositioning time of a patient for irradiation therapy. Motor drivingforce is transmitted to a plurality of leaf plates at the same timethrough a pinion gear. The system also uses upper and lower aircylinders and upper and lower guides to position a patient.

Imaging

P. Adamee, et. al. “Charged Particle Beam Apparatus and Method forOperating the Same”, U.S. Pat. No. 7,274,018 (Sep. 25, 2007) and P.Adamee, et. al. “Charged Particle Beam Apparatus and Method forOperating the Same”, U.S. Pat. No. 7,045,781 (May 16, 2006) describe acharged particle beam apparatus configured for serial and/or parallelimaging of an object.

K. Hiramoto, et. al. “Ion Beam Therapy System and its Couch PositioningSystem”, U.S. Pat. No. 7,193,227 (Mar. 20, 2007) describe a ion beamtherapy system having an X-ray imaging system moving in conjunction witha rotating gantry.

C. Maurer, et. al. “Apparatus and Method for Registration of Images toPhysical Space Using a Weighted Combination of Points and Surfaces”,U.S. Pat. No. 6,560,354 (May 6, 2003) described a process of X-raycomputed tomography registered to physical measurements taken on thepatient's body, where different body parts are given different weights.Weights are used in an iterative registration process to determine arigid body transformation process, where the transformation function isused to assist surgical or stereotactic procedures.

M. Blair, et. al. “Proton Beam Digital Imaging System”, U.S. Pat. No.5,825,845 (Oct. 20, 1998) describe a proton beam digital imaging systemhaving an X-ray source that is movable into the treatment beam line thatcan produce an X-ray beam through a region of the body. By comparison ofthe relative positions of the center of the beam in the patientorientation image and the isocentre in the master prescription imagewith respect to selected monuments, the amount and direction of movementof the patient to make the best beam center correspond to the targetisocentre is determined.

S. Nishihara, et. al. “Therapeutic Apparatus”, U.S. Pat. No. 5,039,867(Aug. 13,1991) describe a method and apparatus for positioning atherapeutic beam in which a first distance is determined on the basis ofa first image, a second distance is determined on the basis of a secondimage, and the patient is moved to a therapy beam irradiation positionon the basis of the first and second distances.

Problem

There exists in the art of particle beam treatment of cancerous tumorsin the body a need for efficient control of magnetic fields used in thecontrol of charged particles in a synchrotron of a charged particlecancer therapy system. Further, there exists in the art of particle beamtherapy of cancerous tumors a need for reduced power supplyrequirements, reduced construction costs, and reduced size of thesynchrotron. Further, there exists a need in the art to control thecharged particle cancer therapy system in terms of specified energy,intensity, and/or timing of charged particle delivery. Still further,there exists a need for efficient, precise, and/or accurate noninvasive,in-vivo treatment of a solid cancerous tumor with minimization of damageto surrounding healthy tissue in a patient.

SUMMARY OF THE INVENTION

The invention comprises intensity control of a charged particle beamacceleration, extraction, and/or targeting method and apparatus used inconjunction with charged particle beam radiation therapy of canceroustumors.

DESCRIPTION OF THE FIGURES

FIG. 1 illustrates component connections of a particle beam therapysystem;

FIG. 2 illustrates a charged particle therapy system;

FIG. 3 illustrates straight and turning sections of a synchrotron

FIG. 4 illustrates turning magnets of a synchrotron;

FIG. 5 provides a perspective view of a turning magnet;

FIG. 6 illustrates a cross-sectional view of a turning magnet;

FIG. 7 illustrates a cross-sectional view of a turning magnet;

FIG. 8 illustrates magnetic field concentration in a turning magnet;

FIG. 9 illustrates correction coils in a turning magnet;

FIG. 10 illustrates a magnetic turning section of a synchrotron;

FIG. 11 illustrates a magnetic field control system;

FIG. 12 illustrates a charged particle extraction and intensity controlsystem;

FIG. 13 illustrates 3-dimensional scanning of a proton beam focal spot,and

FIG. 14 illustrates 4- or 5-dimensional scanning of a charged particlebeam spot.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates generally to treatment of solid cancers. Moreparticularly, the invention relates to intensity control of a chargedparticle stream in a particle accelerator. Magnetic field controlelements and intensity control are used in conjunction with chargedparticle cancer therapy beam acceleration, extraction, and/or targetingmethods and apparatus.

Novel design features of a synchrotron are described. Particularly,intensity control of a charged particle beam acceleration, extraction,and/or targeting method and apparatus used in conjunction with chargedparticle beam radiation therapy of cancerous tumors is described. Moreparticularly, intensity control of a charged particle stream of asynchrotron is described. Intensity control is described in combinationwith turning magnets, edge focusing magnets, concentrating magneticfield magnets, winding and control coils, and extraction elements of thesynchrotron. The system reduces the overall size of the synchrotron,provides a tightly controlled proton beam, directly reduces the size ofrequired magnetic fields, directly reduces required operating power, andallows continual acceleration of protons in a synchrotron even during aprocess of extracting protons from the synchrotron.

Cyclotron/Synchrotron

A cyclotron uses a constant magnetic field and a constant-frequencyapplied electric field. One of the two fields is varied in asynchrocyclotron. Both of these fields are varied in a synchrotron.Thus, a synchrotron is a particular type of cyclic particle acceleratorin which a magnetic field is used to turn the particles so theycirculate and an electric field is used to accelerate the particles. Thesynchroton carefully synchronizes the applied fields with the travellingparticle beam.

By increasing the fields appropriately as the particles gain energy, thecharged particles path can be held constant as they are accelerated.This allows the vacuum container for the particles to be a large thintorus. In practice it is easier to use some straight sections betweenthe bending magnets and some turning sections giving the torus the shapeof a round-cornered polygon. A path of large effective radius is thusconstructed using simple straight and curved pipe segments, unlike thedisc-shaped chamber of the cyclotron type devices. The shape also allowsand requires the use of multiple magnets to bend the particle beam.

The maximum energy that a cyclic accelerator can impart is typicallylimited by the strength of the magnetic fields and the minimumradius/maximum curvature, of the particle path. In a cyclotron themaximum radius is quite limited as the particles start at the center andspiral outward, thus this entire path must be a self-supportingdisc-shaped evacuated chamber. Since the radius is limited, the power ofthe machine becomes limited by the strength of the magnetic field. Inthe case of an ordinary electromagnet, the field strength is limited bythe saturation of the core because when all magnetic domains are alignedthe field may not be further increased to any practical extent. Thearrangement of the single pair of magnets also limits the economic sizeof the device.

Synchrotrons overcome these limitations, using a narrow beam pipesurrounded by much smaller and more tightly focusing magnets. Theability of this device to accelerate particles is limited by the factthat the particles must be charged to be accelerated at all, but chargedparticles under acceleration emit photons, thereby losing energy. Thelimiting beam energy is reached when the energy lost to the lateralacceleration required to maintain the beam path in a circle equals theenergy added each cycle. More powerful accelerators are built by usinglarge radius paths and by using more numerous and more powerfulmicrowave cavities to accelerate the particle beam between corners.Lighter particles, such as electrons, lose a larger fraction of theirenergy when turning. Practically speaking, the energy ofelectron/positron accelerators is limited by this radiation loss, whileit does not play a significant role in the dynamics of proton or ionaccelerators. The energy of those is limited strictly by the strength ofmagnets and by the cost.

Charged Particle Beam Therapy

Throughout this document, a charged particle beam therapy system, suchas a proton beam, hydrogen ion beam, or carbon ion beam, is described.Herein, the charged particle beam therapy system is described using aproton beam. However, the aspects taught and described in terms of aproton beam are not intended to be limiting to that of a proton beam andare illustrative of a charged particle beam system. Any charged particlebeam system is equally applicable to the techniques described herein.

Referring now to FIG. 1, a charged particle beam system 100 isillustrated. The charged particle beam preferably comprises a number ofsubsystems including any of: a main controller 110; an injection system120; a synchrotron 130 that typically includes: (1) an acceleratorsystem 132 and (2) an extraction system 134; a targeting/delivery system140; a patient interface module 150; a display system 160; and/or animaging system 170.

An exemplary method of use of the charged particle beam system 100 isprovided. The main controller 110 controls one or more of the subsystemsto accurately and precisely deliver protons to a tumor of a patient. Forexample, the main controller 110 obtains an image, such as a portion ofa body and/or of a tumor, from the imaging system 170. The maincontroller 110 also obtains position and/or timing information from thepatient interface module 150. The main controller 110 then optionallycontrols the injection system 120 to inject a proton into a synchrotron130. The synchrotron typically contains at least an accelerator system132 and an extraction system 134. The main controller preferablycontrols the proton beam within the accelerator system, such as bycontrolling speed, trajectory, and timing of the proton beam. The maincontroller then controls extraction of a proton beam from theaccelerator through the extraction system 134. For example, thecontroller controls timing, energy, and/or intensity of the extractedbeam. The controller 110 also preferably controls targeting of theproton beam through the targeting/delivery system 140 to the patientinterface module 150. One or more components of the patient interfacemodule 150 are preferably controlled by the main controller 110.Further, display elements of the display system 160 are preferablycontrolled via the main controller 110. Displays, such as displayscreens, are typically provided to one or more operators and/or to oneor more patients. In one embodiment, the main controller 110 times thedelivery of the proton beam from all systems, such that protons aredelivered in an optimal therapeutic manner to the patient. Herein, themain controller 110 refers to a single system controlling the chargedparticle beam system 100, to a single controller controlling a pluralityof subsystems controlling the charged particle beam system 100, or to aplurality of individual controllers controlling one or more sub-systemsof the charged particle beam system 100.

Synchrotron

Herein, the term synchrotron is used to refer to a system maintainingthe charged particle beam in a circulating path; however, cyclotrons arealternatively used, albeit with their inherent limitations of energy,intensity, and extraction control. Further, the charged particle beam isreferred to herein as circulating along a circulating path about acentral point of the synchrotron. The circulating path is alternativelyreferred to as an orbiting path; however, the orbiting path does notrefer a perfect circle or ellipse, rather it refers to cycling of theprotons around a central point or region.

Referring now to FIG. 2, an illustrative exemplary embodiment of oneversion of the charged particle beam system 100 is provided. The number,position, and described type of components is illustrative andnon-limiting in nature. In the illustrated embodiment, the injectionsystem 120 or ion source or charged particle beam source generatesprotons. The protons are delivered into a vacuum tube that runs into,through, and out of the synchrotron. The generated protons are deliveredalong an initial path 262. Focusing magnets 230, such as quadrupolemagnets or injection quadrupole magnets, are used to focus the protonbeam path. A quadrupole magnet is a focusing magnet. An injector bendingmagnet 232 bends the proton beam toward the plane of the synchrotron130. The focused protons having an initial energy are introduced into aninjector magnet 240, which is preferably an injection Lamberson magnet.Typically, the initial beam path 262 is along an axis off of, such asabove, a circulating plane of the synchrotron 130. The injector bendingmagnet 232 and injector magnet 240 combine to move the protons into thesynchrotron 130. Main bending or turning magnets, dipole magnets, orcirculating magnets 250 are used to turn the protons along a circulatingbeam path 264. A dipole magnet is a bending magnet. The main bendingmagnets 250 bend the initial beam path 262 into a circulating beam path264. In this example, the main bending magnets 250 or circulatingmagnets are represented as four sets of four magnets to maintain thecirculating beam path 264 into a stable circulating beam path. However,any number of magnets or sets of magnets are optionally used to move theprotons around a single orbit in the circulation process. The protonspass through an accelerator 270. The accelerator accelerates the protonsin the circulating beam path 264. As the protons are accelerated, thefields applied by the magnets 250 are increased. Particularly, the speedof the protons achieved by the accelerator 270 are synchronized withmagnetic fields of the main bending magnets 250 or circulating magnetsto maintain stable circulation of the protons about a central point orregion 280 of the synchrotron. At separate points in time theaccelerator 270/main bending magnet 250 combination is used toaccelerate and/or decelerate the circulating protons while maintainingthe protons in the circulating path or orbit. An extraction element ofthe inflector/deflector system 290 is used in combination with aLamberson extraction magnet 292 to remove protons from their circulatingbeam path 264 within the synchrotron 130. One example of a deflectorcomponent is a Lamberson magnet. Typically the deflector moves theprotons from the circulating plane to an axis off of the circulatingplane, such as above the circulating plane. Extracted protons arepreferably directed and/or focused using an extraction bending magnet237 and extraction focusing magnets 235, such as quadrupole magnetsalong a transport path 268 into the scanning/targeting/delivery system140. Two components of a scanning system 140 or targeting systemtypically include a first axis control 142, such as a vertical control,and a second axis control 144, such as a horizontal control. In oneembodiment, the first axis control 142 allows for about 100 mm ofvertical or y-axis scanning of the proton beam 268 and the second axiscontrol 144 allows for about 700 mm of horizontal or x-axis scanning ofthe proton beam 268. A nozzle system is optionally used for imaging theproton beam and/or as a vacuum barrier between the low pressure beampath of the synchrotron and the atmosphere. Protons are delivered withcontrol to the patient interface module 150 and to a tumor of a patient.All of the above listed elements are optional and may be used in variouspermutations and combinations. Use of the above listed elements isfurther described, infra. Protons are delivered with control to thepatient interface module 170 and to a tumor of a patient.

In one example, the charged particle irradiation includes a synchrotronhaving: a center, straight sections, and turning sections. The chargedparticle beam path runs about the center, through the straight sections,and through the turning sections, where each of the turning sectionscomprises a plurality of bending magnets. Preferably, the circulationbeam path comprises a length of less than sixty meters, and the numberof straight sections equals the number of turning sections. Preferablyno quadrupoles are used in or around the circulating path of thesynchrotron.

Circulating System

A synchrotron 130 preferably comprises a combination of straightsections 310 and ion beam turning sections 320. Hence, the circulatingpath of the protons is not circular in a synchrotron, but is rather apolygon with rounded corners.

In one illustrative embodiment, the synchrotron 130, which is alsoreferred to as an accelerator system, has four straight elements andfour turning sections. Examples of straight sections 310 include the:inflector 240, accelerator 270, extraction system 290, and deflector292. Along with the four straight sections are four ion beam turningsections 320, which are also referred to as magnet sections or turningsections. Turning sections are further described, infra.

Referring now to FIG. 3, an exemplary synchrotron is illustrated. Inthis example, protons delivered along the initial path 262 are inflectedinto the circulating beam path with the inflector 240 and afteracceleration are extracted via a deflector 292 to a beam transport path268. In this example, the synchrotron 130 comprises four straightsections 310 and four turning sections 320 where each of the fourturning sections use one or more magnets to turn the proton beam aboutninety degrees. As is further described, infra, the ability to closelyspace the turning sections and efficiently turn the proton beam resultsin shorter straight sections. Shorter straight sections allows for asynchrotron design without the use of focusing quadrupoles in thecirculating beam path of the synchrotron. The removal of the focusingquadrupoles from the circulating proton beam path results in a morecompact design. In this example, the illustrated synchrotron has about afive meter diameter versus eight meter and larger cross-sectionaldiameters for systems using a quadrupole focusing magnet in thecirculating proton beam path.

Referring now to FIG. 4, additional description of the first turningsection 320 is provided. Each of the turning sections preferablycomprises multiple magnets, such as about 2, 4, 6, 8, 10, or 12 magnets.In this example, four turning magnets 410, 420, 430, 440 in the firstturning section 320 are used to illustrate key principles, which are thesame regardless of the number of magnets in a turning section 320. Aturning magnet 410 is a particular type of circulating magnet 250.

In physics, the Lorentz force is the force on a point charge due toelectromagnetic fields. The Lorentz force is given by the equation 1 interms of magnetic fields with the election field terms not included.

F=q(v×B)   eq. 1

In equation 1, F is the force in newtons; B is the magnetic field inTeslas; and v is the instantaneous velocity of the particles in metersper second.

Referring now to FIG. 5, an example of a single magnet turning section410 is expanded. The turning section includes a gap 510. The gap ispreferably a flat gap, allowing for a magnetic field across the gap thatis more uniform, even, and intense. A magnetic field enters the gapthrough a magnetic field incident surface and exits the gap through amagnetic field exiting surface. The gap 510 runs in a vacuum tubebetween two magnet halves. The gap is controlled by at least twoparameters: (1) the gap 510 is kept as large as possible to minimizeloss of protons and (2) the gap 510 is kept as small as possible tominimize magnet sizes and the associated size and power requirements ofthe magnet power supplies. The flat nature of the gap 510 allows for acompressed and more uniform magnetic field across the gap. One exampleof a gap dimension is to accommodate a vertical proton beam size ofabout 2 cm with a horizontal beam size of about 5 to 6 cm.

As described, supra, a larger gap size requires a larger power supply.For instance, if the gap size doubles in vertical size, then the powersupply requirements increase by about a factor of four. The flatness ofthe gap is also important. For example, the flat nature of the gapallows for an increase in energy of the extracted protons from about 250to about 330 MeV. More particularly, if the gap 510 has an extremelyflat surface, then the limits of a magnetic field of an iron magnet arereachable. An exemplary precision of the flat surface of the gap 510 isa polish of less than about five microns and preferably with a polish ofabout one to three microns. Unevenness in the surface results inimperfections in the applied magnetic field. The polished flat surfacespreads unevenness of the applied magnetic field.

Still referring to FIG. 5, the charged particle beam moves through thegap with an instantaneous velocity, v. A first magnetic coil 520 and asecond magnetic coil 530 run above and below the gap 510, respectively.Current running through the coils 520, 530 results in a magnetic field,B, running through the single magnet turning section 410. In thisexample, the magnetic field, B, runs upward, which results in a force,F, pushing the charged particle beam inward toward a central point ofthe synchrotron, which turns the charged particle beam in an arc.

Still referring to FIG. 5, a portion of an optional second magnetturning section 420 is illustrated. The coils 520, 530 typically havereturn elements or turns at the end of one magnet, such as at the end ofthe first magnet turning section 410. The return elements take space.The space reduces the percentage of the path about one orbit of thesynchrotron that is covered by the turning magnets. This leads toportions of the circulating path where the protons are not turned and/orfocused and allows for portions of the circulating path where the protonpath defocuses. Thus, the space results in a larger synchrotron.Therefore, the space between magnet turning sections 560 is preferablyminimized. The second turning magnet is used to illustrate that thecoils 520, 530 optionally run along a plurality of magnets, such as 2,3, 4, 5, 6, or more magnets. Coils 520, 530 running across turningsection magnets allows for two turning section magnets to be spatiallypositioned closer to each other due to the removal of the stericconstraint of the turns, which reduces and/or minimizes the space 560between two turning section magnets.

Referring now to FIGS. 6 and 7, two illustrative 90 degree rotatedcross-sections of single magnet turning sections 410 are presented. Themagnet assembly has a first magnet 610 and a second magnet 620. Amagnetic field induced by coils, described infra, runs between the firstmagnet 610 to the second magnet 620 across the gap 510. Return magneticfields run through a first yoke 612 and second yoke 622. The chargedparticles run through the vacuum tube in the gap. As illustrated,protons run into FIG. 6 through the gap 510 and the magnetic field,illustrated as vector B, applies a force F to the protons pushing theprotons towards the center of the synchrotron, which is off page to theright in FIG. 6. The magnetic field is created using windings. A firstcoil of wire is wound around the magnet to yield a first winding coil650. The second coil of wire is wound to around the second magnet toyield a second winding coil 660. Isolating gaps 630, 640, such as airgaps, isolate the iron based yokes 612, 622 from the gap 510. The gap isapproximately flat to yield a uniform magnetic field across the gap, asdescribed supra.

Referring again to FIG. 7, the ends of a single turning magnet arepreferably beveled. Nearly perpendicular or right angle edges of aturning magnet 410 are represented by a dashed lines 674, 684.Preferably, the edge of the turning magnet is beveled at angles alpha,α, and beta, β, which is the off perpendicular angle between the rightangles 674, 684 and beveled edges 672, 682. The angle alpha is used todescribe the effect and the description of angle alpha applies to anglebeta, but angle alpha is optionally different from angle beta. The anglealpha provides an edge focusing effect. Beveling the edge of the turningmagnet 410 at angle alpha focuses the proton beam.

Multiple turning magnets provide multiple magnet edges that each haveedge focusing effects in the synchrotron 310. If only one turning magnetis used, then the beam is only focused once for angle alpha or twice forangle alpha and angle beta. However, by using smaller turning magnets,more turning magnets fit into the turning sections 320 of thesynchrotron 310. For example, if four magnets are used in a turningsection 320 of the synchrotron, then there are eight possible edgefocusing effect surfaces, two edges per magnet. The eight focusingsurfaces yield a smaller cross-sectional beam size. This allows the useof a smaller gap 510.

The use of multiple edge focusing effects in the turning magnets resultsin not only a smaller gap, but also the use of smaller magnets andsmaller power supplies. For a synchrotron 310 having four turningsections 320 where each turning sections has four turning magnets andeach turning magnet has two focusing edges, a total of thirty-twofocusing edges exist for each orbit of the protons in the circulatingpath of the synchrotron 310. Similarly, if 2, 6, or 8 magnets are usedin a given turning section, or if 2, 3, 5, or 6 turning sections areused, then the number of edge focusing surfaces expands or contractsaccording to equation 2.

$\begin{matrix}{{TFE} = {{NTS} \star \frac{M}{NTS} \star \frac{FE}{M}}} & {{eq}.\mspace{14mu} 2}\end{matrix}$

where TFE is the number of total focusing edges, NTS is the number ofturning section, M is the number of magnets, and FE is the number offocusing edges. Naturally, not all magnets are necessarily beveled andsome magnets are optionally beveled on only one edge.

The inventors have determined that multiple smaller magnets havebenefits over fewer larger magnets. For example, the use of 16 smallmagnets yields 32 focusing edges whereas the use of 4 larger magnetsyields only 8 focusing edges. The use of a synchrotron having morefocusing edges results in a circulating path of the synchrotron builtwithout the use of focusing quadrupoles magnets. All prior artsynchrotrons use quadrupoles in the circulating path of the synchrotron.Further, the use of quadrupoles in the circulating path necessitatesadditional straight sections in the circulating path of the synchrotron.Thus, the use of quadrupoles in the circulating path of a synchrotronresults in synchrotrons having larger diameters or largercircumferences.

In various embodiments of the system described herein, the synchrotronhas:

-   -   at least 4 and preferably 6, 8, 10, or more edge focusing edges        per 90 degrees of turn of the charged particle beam in a        synchrotron having four turning sections;    -   at least about 16 and preferably about 24, 32, or more edge        focusing edges per orbit of the charged particle beam in the        synchrotron;    -   only 4 turning sections where each of the turning sections        includes at least 4 and preferably 8 edge focusing edges;    -   an equal number of straight sections and turning sections;    -   exactly 4 turning sections;    -   at least 4 edge focusing edges per turning section;    -   no quadrupoles in the circulating path of the synchrotron;    -   a rounded corner rectangular polygon configuration;    -   a circumference of less than 60 meters;    -   a circumference of less than 60 meters and 32 edge focusing        surfaces; and/or    -   any of about 8, 16, 24, or 32 non-quadrupole magnets per        circulating path of the synchrotron, where the non-quadrupole        magnets include edge focusing edges.

Referring now to FIG. 6, the incident magnetic field surface 670 of thefirst magnet 610 is further described. FIG. 6 is not to scale and isillustrative in nature. Local imperfections or unevenness in quality ofthe finish of the incident surface 670 results in inhomogeneities orimperfections in the magnetic field applied to the gap 510. Preferably,the incident surface 670 is flat, such as to within about a zero tothree micron finish polish, or less preferably to about a ten micronfinish polish.

Referring now to FIG. 8, additional magnet elements, of the magnetcross-section illustratively represented in FIG. 6, are described. Thefirst magnet 610 preferably contains an initial cross-sectional distance810 of the iron based core. The contours of the magnetic field areshaped by the magnets 610, 620 and the yokes 612, 622. The iron basedcore tapers to a second cross-sectional distance 820. The magnetic fieldin the magnet preferentially stays in the iron based core as opposed tothe gaps 630, 640. As the cross-sectional distance decreases from theinitial cross-sectional distance 810 to the final cross-sectionaldistance 820, the magnetic field concentrates. The change in shape ofthe magnet from the longer distance 810 to the smaller distance 820 actsas an amplifier. The concentration of the magnetic field is illustratedby representing an initial density of magnetic field vectors 830 in theinitial cross-section 810 to a concentrated density of magnetic fieldvectors 840 in the final cross-section 820. The concentration of themagnetic field due to the geometry of the turning magnets results infewer winding coils 650, 660 being required and also a smaller powersupply to the coils being required.

Example I

In one example, the initial cross-section distance 810 is about fifteencentimeters and the final cross-section distance 820 is about tencentimeters. Using the provided numbers, the concentration of themagnetic field is about 15/10 or 1.5 times at the incident surface 670of the gap 510, though the relationship is not linear. The taper 860 hasa slope, such as about 20 to 60 degrees. The concentration of themagnetic field, such as by 1.5 times, leads to a corresponding decreasein power consumption requirements to the magnets.

Referring now to FIG. 9, an additional example of geometry of the magnetused to concentrate the magnetic field is illustrated. As illustrated inFIG. 8, the first magnet 610 preferably contains an initialcross-sectional distance 810 of the iron based core. The contours of themagnetic field are shaped by the magnets 610, 620 and the yokes 612,622. In this example, the core tapers to a second cross-sectionaldistance 820 with a smaller angle theta, θ. As described, supra, themagnetic field in the magnet preferentially stays in the iron based coreas opposed to the gaps 630, 640. As the cross-sectional distancedecreases from the initial cross-sectional distance 810 to the finalcross-sectional distance 820, the magnetic field concentrates. Thesmaller angle, theta, results in a greater amplification of the magneticfield in going from the longer distance 810 to the smaller distance 820.The concentration of the magnetic field is illustrated by representingan initial density of magnetic field vectors 830 in the initialcross-section 810 to a concentrated density of magnetic field vectors840 in the final cross-section 820. The concentration of the magneticfield due to the geometry of the turning magnets results in fewerwinding coils 650, 660 being required and also a smaller power supply tothe winding coils 650, 660 being required.

Still referring to FIG. 9, optional correction coils 910, 920 areillustrated that are used to correct the strength of one or more turningmagnets. The correction coils 920, 930 supplement the winding coils 650,660. The correction coils 910, 920 have correction coil power suppliesthat are separate from winding coil power supplies used with the windingcoils 650, 660. The correction coil power supplies typically operate ata fraction of the power required compared to the winding coil powersupplies, such as about 1, 2, 3, 5, 7, or 10 percent of the power andmore preferably about 1 or 2 percent of the power used with the windingcoils 650, 660. The smaller operating power applied to the correctioncoils 920, 920 allows for more accurate and/or precise control of thecorrection coils. The correction coils are used to adjust forimperfection in the turning magnets 410, 420, 430, 440.

Referring now to FIG. 10, an example of winding coils and correctioncoils about a plurality of turning magnets in an ion beam turningsection is illustrated. The winding coils preferably cover 1, 2, or 4turning magnets. In the illustrated example, a winding coil 1030 windsaround two turning magnets 410, 420 generating a magnetic field.Correction coils are used to correct the magnetic field strength of oneor more turning or bending magnets. In the illustrated example, a firstcorrection coil 1010 corrects a single turning magnet. Combined in theillustration, but separately implemented, a second correction coil 1020corrects two turning magnets 410, 420. The correction coils supplementthe winding coils. The correction coils have correction coil powersupplies that are separate from winding coil power supplies used withthe winding coils. The correction coil power supplies typically operateat a fraction of the power required compared to the winding coil powersupplies, such as about 1, 2, 3, 5, 7, or 10 percent of the power andmore preferably about 1 or 2 percent of the power used with the windingcoils. The smaller operating power applied to the correction coilsallows for more accurate and/or precise control of the correction coils.More particularly, a magnetic field produced by the first correctioncoil 1010 is used to adjust for imperfection in a magnetic filedproduced by the turning magnet 410 or the second correction coil 1020 isused to adjust for imperfection in the turning magnet sections 610, 620.Optionally, separate correction coils are used for each turning magnetallowing individual tuning of the magnetic field for each turningmagnet, which eases quality requirements in the manufacture of eachturning magnet.

Correction coils are preferably used in combination with magnetic fieldconcentration magnets to stabilize a magnetic field in a synchrotron.For example, high precision magnetic field sensors 1050 are used tosense a magnetic field created in one or more turning magnets usingwinding elements. The sensed magnetic field is sent via a feedback loopto a magnetic field controller that adjusts power supplied to correctioncoils. The correction coils, operating at a lower power, are capable ofrapid adjustment to a new power level. Hence, via the feedback loop, thetotal magnetic field applied by the turning magnets and correction coilsis rapidly adjusted to a new strength, allowing continuous adjustment ofthe energy of the proton beam. In further combination, a novelextraction system allows the continuously adjustable energy level of theproton beam to be extracted from the synchrotron.

For example, one or more high precision magnetic field sensors 1050 areplaced into the synchrotron and are used to measure the magnetic fieldat or near the proton beam path. For example, the magnetic sensors areoptionally placed between turning magnets and/or within a turningmagnet, such as at or near the gap 510 or at or near the magnet core oryoke. The sensors are part of a feedback system to the correction coils,which is optionally run by the main controller 110. The feedback systemis controlled by the main controller 110 or a subunit or sub-function ofthe main controller 110. Thus, the system preferably stabilizes themagnetic field in the synchrotron elements rather than stabilizing thecurrent applied to the magnets. Stabilization of the magnetic fieldallows the synchrotron to come to a new energy level quickly.

Optionally, the one or more high precision magnetic field sensors areused to coordinate synchrotron beam energy and timing with patientrespiration. Stabilization of the magnetic field allows the synchrotronto come to a new energy level quickly. This allows the system to becontrolled to an operator or algorithm selected energy level with eachpulse of the synchrotron and/or with each breath of the patient.

The winding and/or correction coils correct 1, 2, 3, or 4 turningmagnets, and preferably correct a magnetic field generated by twoturning magnets. A winding or correction coil covering multiple magnetsreduces space between magnets as fewer winding or correction coil endsare required, which occupy space.

Example II

Referring now to FIG. 11, an example is used to clarify the magneticfield control using a feedback loop 1100 to change delivery times and/orperiods of proton pulse delivery. In one case, a respiratory sensor 1110senses the breathing cycle of the subject. The respiratory sensor sendsthe information to an algorithm in a magnetic field controller 1120,typically via the patient interface module 150 and/or via the maincontroller 110 or a subcomponent thereof. The algorithm predicts and/ormeasures when the subject is at a particular point in the breathingcycle, such as at the bottom of a breath. Magnetic field sensors 1130,such as the high precision magnetic field sensors 1050, are used asinput to the magnetic field controller, which controls a magnet powersupply 1140 for a given magnetic field 1150, such as within a firstturning magnet 410 of a synchrotron 130. The control feedback loop isthus used to dial the synchrotron to a selected energy level and deliverprotons with the desired energy at a selected point in time, such as atthe bottom of the breath. More particularly, the synchrotron acceleratesthe protons and the control feedback loop keeps the protons in thecirculating path by synchronously adjusting the magnetic field strengthof the turning magnets. Intensity of the proton beam is also selectableat this stage. The feedback control to the correction coils allows rapidselection of energy levels of the synchrotron that are tied to thepatient's breathing cycle. This system is in stark contrast to a systemwhere the current is stabilized and the synchrotron deliver pulses witha period, such as 10 or 20 cycles second with a fixed period.

The feedback or the magnetic field design coupled with the correctioncoils allows for the extraction cycle to match the varying respiratoryrate of the patient.

Traditional extraction systems do not allow this control as magnets havememories in terms of both magnitude and amplitude of a sine wave. Hence,in a traditional system, in order to change frequency, slow changes incurrent must be used. However, with the use of the feedback loop usingthe magnetic field sensors, the frequency and energy level of thesynchrotron are rapidly adjustable. Further aiding this process is theuse of a novel extraction system that allows for acceleration of theprotons during the extraction process, described infra.

Example III

Referring again to FIG. 10, an example of a winding coil 1030 thatcovers two turning magnets 410, 420 is provided. As described, supra,this system reduces space between turning section allowing more magneticfield to be applied per radian of turn. A first correction coil 1010 isillustrated that is used to correct the magnetic field for the firstturning magnet 410. Individual correction coils for each turning magnetare preferred and individual correction coils yield the most preciseand/or accurate magnetic field in each turning section. Particularly,the individual correction coil 1010 is used to compensate forimperfections in the individual magnet of a given turning section.Hence, with a series of magnetic field sensors, corresponding magneticfields are individually adjustable in a series of feedback loops, via amagnetic field monitoring system 1030, as an independent coil is usedfor each turning section magnet. Alternatively, a multiple magnetcorrection coil 1020 is used to correct the magnetic field for aplurality of turning section magnets.

Flat Gap Surface

While the gap surface is described in terms of the first turning magnet410, the discussion applies to each of the turning magnets in thesynchrotron. Similarly, while the gap 510 surface is described in termsof the magnetic field incident surface 670, the discussion additionallyoptionally applies to the magnetic field exiting surface 680.

The magnetic field incident surface 670 of the first magnet 610 ispreferably about flat, such as to within about a zero to three micronfinish polish or less preferably to about a ten micron finish polish. Bybeing very flat, the polished surface spreads the unevenness of theapplied magnetic field across the gap 510. The very flat surface, suchas about 0, 1, 2, 4, 6, 8, 10, 15, or 20 micron finish, allows for asmaller gap size, a smaller applied magnetic field, smaller powersupplies, and tighter control of the proton beam cross-sectional area.

Proton Beam Extraction

Referring now to FIG. 12, an exemplary proton extraction process fromthe synchrotron 130 is illustrated. For clarity, FIG. 12 removeselements represented in FIG. 2, such as the turning magnets, whichallows for greater clarity of presentation of the proton beam path as afunction of time. Generally, protons are extracted from the synchrotron130 by slowing the protons. As described, supra, the protons wereinitially accelerated in a circulating path 264, which is maintainedwith a plurality of turning magnets 250. The circulating path isreferred to herein as an original central beamline 264. The protonsrepeatedly cycle around a central point in the synchrotron 280. Theproton path traverses through an RF cavity system 1210. To initiateextraction, an RF field is applied across a first blade 1212 and asecond blade 1214, in the RF cavity system 1210. The first blade 1212and second blade 1214 are referred to herein as a first pair of blades.

In the proton extraction process, a radio-frequency (RF) voltage isapplied across the first pair of blades, where the first blade 1212 ofthe first pair of blades is on one side of the circulating proton beampath 264 and the second blade 1214 of the first pair of blades is on anopposite side of the circulating proton beam path 264. The applied RFfield applies energy to the circulating charged-particle beam. Theapplied RF field alters the orbiting or circulating beam path slightlyof the protons from the original central beamline 264 to an alteredcirculating beam path 265. Upon a second pass of the protons through theRF cavity system, the RF field further moves the protons off of theoriginal proton beamline 264. For example, if the original beamline isconsidered as a circular path, then the altered beamline is slightlyelliptical. The applied RF field is timed to apply outward or inwardmovement to a given band of protons circulating in the synchrotronaccelerator. Each orbit of the protons is slightly more off axiscompared to the original circulating beam path 264. Successive passes ofthe protons through the RF cavity system are forced further and furtherfrom the original central beamline 264 by altering the direction and/orintensity of the RF field with each successive pass of the proton beamthrough the RF field.

The RF voltage is frequency modulated at a frequency about equal to theperiod of one proton cycling around the synchrotron for one revolutionor at a frequency than is an integral multiplier of the period of oneproton cycling about the synchrotron. The applied RF frequency modulatedvoltage excites a betatron oscillation. For example, the oscillation isa sine wave motion of the protons. The process of timing the RF field toa given proton beam within the RF cavity system is repeated thousands oftimes with successive passes of the protons being moved approximatelyone micrometer further off of the original central beamline 264. Forclarity, the effect of the approximately 1000 changing beam paths witheach successive path of a given band of protons through the RF field areillustrated as the altered beam path 265.

With a sufficient sine wave betatron amplitude, the altered circulatingbeam path 265 touches a material 1230, such as a foil or a sheet offoil. The foil is preferably a lightweight material, such as beryllium,a lithium hydride, a carbon sheet, or a material of low nuclear charge.A material of low nuclear charge is a material composed of atomsconsisting essentially of atoms having six or fewer protons. The foil ispreferably about 10 to 150 microns thick, is more preferably 30 to 100microns thick, and is still more preferably 40-60 microns thick. In oneexample, the foil is beryllium with a thickness of about 50 microns.When the protons traverse through the foil, energy of the protons islost and the speed of the protons is reduced. Typically, a current isalso generated, described infra. Protons moving at a slower speed travelin the synchrotron with a reduced radius of curvature 266 compared toeither the original central beamline 264 or the altered circulating path265. The reduced radius of curvature 266 path is also referred to hereinas a path having a smaller diameter of trajectory or a path havingprotons with reduced energy. The reduced radius of curvature 266 istypically about two millimeters less than a radius of curvature of thelast pass of the protons along the altered proton beam path 265.

The thickness of the material 1230 is optionally adjusted to created achange in the radius of curvature, such as about ½, 1, 2, 3, or 4 mmless than the last pass of the protons 265 or original radius ofcurvature 264. Protons moving with the smaller radius of curvaturetravel between a second pair of blades. In one case, the second pair ofblades is physically distinct and/or are separated from the first pairof blades. In a second case, one of the first pair of blades is also amember of the second pair of blades. For example, the second pair ofblades is the second blade 1214 and a third blade 1216 in the RF cavitysystem 1210. A high voltage DC signal, such as about 1 to 5 kV, is thenapplied across the second pair of blades, which directs the protons outof the synchrotron through a deflector 292, such as a Lamberson magnet,into a transport path 268.

Control of acceleration of the charged particle beam path in thesynchrotron with the accelerator and/or applied fields of the turningmagnets in combination with the above described extraction system allowsfor control of the intensity of the extracted proton beam, whereintensity is a proton flux per unit time or the number of protonsextracted as a function of time. For example, when a current is measuredbeyond a threshold, the RF field modulation in the RF cavity system isterminated or reinitiated to establish a subsequent cycle of proton beamextraction. This process is repeated to yield many cycles of proton beamextraction from the synchrotron accelerator.

Because the extraction system does not depend on any change any changein magnetic field properties, it allows the synchrotron to continue tooperate in acceleration or deceleration mode during the extractionprocess. Stated differently, the extraction process does not interferewith synchrotron. In stark contrast, traditional extraction systemsintroduce a new magnetic field, such as via a hexapole, during theextraction process. More particularly, traditional synchrotrons have amagnet, such as a hexapole magnet, that is off during an accelerationstage. During the extraction phase, the hexapole magnetic field isintroduced to the circulating path of the synchrotron. The introductionof the magnetic field necessitates two distinct modes, an accelerationmode and an extraction mode, which are mutually exclusive in time.

Charged Particle Beam Intensity Control

Control of applied field, such as a radio-frequency (RF) field,frequency and magnitude in the RF cavity system 1210 allows forintensity control of the extracted proton beam, where intensity isextracted proton flux per unit time or the number of protons extractedas a function of time.

Referring still to FIG. 12, when protons in the proton beam hit thematerial 1230 electrons are given off resulting in a current. Theresulting current is converted to a voltage and is used as part of a ionbeam intensity monitoring system or as part of an ion beam feedback loopfor controlling beam intensity. The voltage is optionally measured andsent to the main controller 110 or to a controller subsystem 1240. Moreparticularly, when protons in the charged particle beam path passthrough the material 1230, some of the protons lose a small fraction oftheir energy, such as about one-tenth of a percent, which results in asecondary electron. That is, protons in the charged particle beam pushsome electrons when passing through material 1230 giving the electronsenough energy to cause secondary emission. The resulting electron flowresults in a current or signal that is proportional to the number ofprotons going through the target material 1230. The resulting current ispreferably converted to voltage and amplified. The resulting signal isreferred to as a measured intensity signal.

The amplified signal or measured intensity signal resulting from theprotons passing through the material 1230 is preferably used incontrolling the intensity of the extracted protons. For example, themeasured intensity signal is compared to a target signal or goal signal,which is predetermined in an irradiation of the tumor plan. Thedifference between the measured intensity signal and the planned forgoal signal is calculated. The difference is used as a control to the RFgenerator. Hence, the measured flow of current resulting from theprotons passing through the material 1230 is used as a control in the RFgenerator to increase or decrease the number of protons undergoingbetatron oscillation and striking the material 1230. Hence, the voltagedetermined off of the material 1230 is used as a measure of the orbitalpath and is used as a feedback control to control the RF cavity system.Alternatively, the measured intensity signal is not used in the feedbackcontrol and is just used as a monitor of the intensity of the extractedprotons.

As described, supra, the photons striking the material 1230 is a step inthe extraction of the protons from the synchrotron 130. Hence, themeasured intensity signal is used to change the number of protons perunit time being extracted, which is referred to as intensity of theproton beam. The intensity of the proton beam is thus under algorithmcontrol. Further, the intensity of the proton beam is controlledseparately from the velocity of the protons in the synchrotron 130.Hence, intensity of the protons extracted and the energy of the protonsextracted are independently variable.

For example, protons initially move at an equilibrium trajectory in thesynchrotron 130. An RF field is used to excite the protons into abetatron oscillation. In one case, the frequency of the protons orbit isabout 10 MHz. In one example, in about one millisecond or after about10,000 orbits, the first protons hit an outer edge of the targetmaterial 130. The specific frequency is dependent upon the period of theorbit. Upon hitting the material 130, the protons push electrons throughthe foil to produce a current. The current is converted to voltage andamplified to yield a measured intensity signal. The measured intensitysignal is used as a feedback input to control the applied RF magnitude,RF frequency, or RF field. Preferably, the measured intensity signal iscompared to a target signal and a measure of the difference between themeasured intensity signal and target signal is used to adjust theapplied RF field in the RF cavity system 1210 in the extraction systemto control the intensity of the protons in the extraction step. Statedagain, the signal resulting from the protons striking and/or passingthrough the material 130 is used as an input in RF field modulation. Anincrease in the magnitude of the RF modulation results in protonshitting the foil or material 130 sooner. By increasing the RF, moreprotons are pushed into the foil, which results in an increasedintensity, or more protons per unit time, of protons extracted from thesynchrotron 130.

In another example, a detector external to the synchrotron 130 is usedto determine the flux of protons extracted from the synchrotron and asignal from the external detector is used to alter the RF field or RFmodulation in the RF cavity system 1210. Here the external detectorgenerates an external signal, which is used in a manner similar to themeasured intensity signal, described in the preceding paragraphs.

In yet another example, when a current from material 130 resulting fromprotons passing through or hitting material is measured beyond athreshold, the RF field modulation in the RF cavity system is terminatedor reinitiated to establish a subsequent cycle of proton beamextraction. This process is repeated to yield many cycles of proton beamextraction from the synchrotron accelerator.

In still yet another embodiment, intensity modulation of the extractedproton beam is controlled by the main controller 110. The maincontroller 110 optionally and/or additionally controls timing ofextraction of the charged particle beam and energy of the extractedproton beam.

In yet still another embodiment, a method or apparatus for controllingintensity of charged particles extracted from a circulating chargedparticle beam path in a synchrotron includes: a radio-frequency fieldgenerator, where during use said radio-frequency generator applies aradio-frequency field to the circulating charged particles yieldingbetatron oscillating charged particles; an extraction material, where atleast a portion of the betatron oscillating charged particles passthrough the extraction material resulting in a secondary emissionelectron flow; an intensity sensor for determining a measure of theelectron flow; and a feedback control loop providing the measure ofelectron flow as a feedback to the radio-frequency generator.Preferably, the target signal calculates a difference between themeasure of the electron flow and the target signal, where the intensitycontroller alters amplitude of the radio-frequency field based upon saiddifference, which results in control of intensity of the extractedcharged particles.

In yet still an additional embodiment, a method or apparatus forextracting intensity controlled charged particles from charged particlescirculating in a synchrotron of a charged particle cancer therapysystem, includes: oscillation blades with a radio-frequency voltageacross the for inducing oscillating charged particles from the chargedparticles circulating in the synchrotron; an extraction material wherethe oscillating charged particles traverse the extraction materialduring use generating both reduced energy charged particles andsecondary emission electrons or a current; and extraction blades used inextracting the energy controlled and intensity controlled chargedparticles from the synchrotron. Preferably, the system includes afeedback intensity controller that generates a measure of the secondaryemission electrons, compares the measure and a target signal, such as anirradiation plan signal 1260 for each beam position striking the tumor1101, and having the intensity controller adjusts amplitude of theradio-frequency voltage based on the comparison yielding intensitycontrolled and energy controlled extracted charged particles.

The benefits of the system include a multi-dimensional scanning system.Particularly, the system allows independence in: (1) energy of theprotons extracted and (2) intensity of the protons extracted. That is,energy of the protons extracted is controlled by an energy controlsystem and an intensity control system controls the intensity of theextracted protons. The energy control system and intensity controlsystem are optionally independently controlled. Preferably, the maincontroller 110 controls the energy control system and the maincontroller simultaneously controls the intensity control system to yieldan extracted proton beam with controlled energy and controlled intensitywhere the controlled energy and controlled intensity are independentlyvariable. Thus the irradiation spot hitting the tumor is underindependent control of:

-   -   time;    -   energy;    -   intensity;    -   x-axis position, where the x-axis represents horizontal movement        of the proton beam relative to the patient, and    -   y-axis position, where the y-axis represents vertical movement        of the proton beam relative to the patient.

In addition, the patient is optionally independently rotated relative toa translational axis of the proton beam at the same time.

Proton Beam Position Control

Referring now to FIG. 13, a beam delivery and tissue volume scanningsystem is illustrated. Presently, the worldwide radiotherapy communityuses a method of dose field forming using a pencil beam scanning system.In stark contrast, FIG. 13 illustrates a spot scanning system or tissuevolume scanning system. In the tissue volume scanning system, the protonbeam is controlled, in terms of transportation and distribution, usingan inexpensive and precise scanning system. The scanning system is anactive system, where the beam is focused into a spot focal point ofabout one-half, one, two, or three millimeters in diameter. The focalpoint is translated along two axes while simultaneously altering theapplied energy of the proton beam, which effectively changes the thirddimension of the focal point. For example, in the illustrated system inFIG. 13, the spot is translated up a vertical axis, is movedhorizontally, and is then translated down a vertical axis. In thisexample, current is used to control a vertical scanning system having atleast one magnet. The applied current alters the magnetic field of thevertical scanning system to control the vertical deflection of theproton beam. Similarly, a horizontal scanning magnet system controls thehorizontal deflection of the proton beam. The degree of transport alongeach axes is controlled to conform to the tumor cross-section at thegiven depth. The depth is controlled by changing the energy of theproton beam. For example, the proton beam energy is decreased, so as todefine a new penetration depth, and the scanning process is repeatedalong the horizontal and vertical axes covering a new cross-sectionalarea of the tumor. Combined, the three axes of control allow scanning ormovement of the proton beam focal point over the entire volume of thecancerous tumor. The time at each spot and the direction into the bodyfor each spot is controlled to yield the desired radiation does at eachsub-volume of the cancerous volume while distributing energy hittingoutside of the tumor.

The focused beam spot volume dimension is preferably tightly controlledto a diameter of about 0.5, 1, or 2 millimeters, but is alternativelyseveral centimeters in diameter. Preferred design controls allowscanning in two directions with: (1) a vertical amplitude of about 100mm amplitude and frequency up to 200 Hz; and (2) a horizontal amplitudeof about 700 mm amplitude and frequency up to 1 Hz. More or lessamplitude in each axis is possible by altering the scanning magnetsystems.

In FIG. 13, the proton beam goes along a z-axis controlled by the beamenergy, the horizontal movement is along an x-axis, and the verticaldirection is along a y-axis. The distance the protons move along thez-axis into the tissue, in this example, is controlled by the kineticenergy of the proton. This coordinate system is arbitrary and exemplary.The actual control of the proton beam is controlled in 3-dimensionalspace using two scanning magnet systems and by controlling the kineticenergy of the proton beam. The use of the extraction system, describedsupra, allows for different scanning patterns. Particularly, the systemallows simultaneous adjustment of the x-, y-, and z-axes in theirradiation of the solid tumor. Stated again, instead of scanning alongan x,y-plane and then adjusting energy of the protons, such as with arange modulation wheel, the system allows for moving along the z-axeswhile simultaneously adjusting the x- and or y-axes. Hence, rather thanirradiating slices of the tumor, the tumor is optionally irradiated inthree simultaneous dimensions. For example, the tumor is irradiatedaround an outer edge of the tumor in three dimensions. Then the tumor isirradiated around an outer edge of an internal section of the tumor.This process is repeated until the entire tumor is irradiated. The outeredge irradiation is preferably coupled with simultaneous rotation of thesubject, such as about a vertical y-axis. This system allows for maximumefficiency of deposition of protons to the tumor, as defined using theBragg peak, to the tumor itself with minimal delivery of proton energyto surrounding healthy tissue.

Combined, the system allows for multi-axes control of the chargedparticle beam system in a small space with low power supply. Forexample, the system uses multiple magnets where each magnet has at leastone edge focusing effect in each turning section of the synchrotronand/or multiple magnets having concentrating magnetic field geometry, asdescribed supra. The multiple edge focusing effects in the circulatingbeam path of the synchrotron combined with the concentration geometry ofthe magnets and described extraction system yields a synchrotron having:

-   -   a small circumference system, such as less than about 50 meters;    -   a vertical proton beam size gap of about 2 cm;    -   corresponding reduced power supply requirements associated with        the reduced gap size;    -   an extraction system not requiring a newly introduced magnetic        field;    -   acceleration or deceleration of the protons during extraction;    -   control z-axis energy during extraction; and    -   simultaneous variation of z-axis energy during extraction.

The result is a 3-dimensional scanning system, x-, y-, and z-axescontrol, where the z-axes control resides in the synchrotron and wherethe z-axes energy is variably controlled during the extraction processinside the synchrotron.

Referring now to FIG. 14, an example of a targeting system 140 used todirect the protons to the tumor with 4-dimensional scanning control isprovided, where the 4-dimensional scanning control is along the x-, y-,and z-axes along with intensity control, as described supra. Typically,charged particles traveling along the transport path 268 are directedthrough a first axis control element 142, such as a vertical control,and a second axis control element 144, such as a horizontal control andinto a tumor 1101. As described, supra, the extraction system alsoallows for simultaneous variation in the z-axis. Further, as describe,supra, the intensity or dose of the extracted beam is optionallysimultaneously and independently controlled and varied. Thus instead ofirradiating a slice of the tumor, as in FIG. 13, all four dimensionsdefining the targeting spot of the proton delivery in the tumor aresimultaneously variable. The simultaneous variation of the protondelivery spot is illustrated in FIG. 14 by the spot delivery path 269.In the illustrated case, the protons are initially directed around anouter edge of the tumor and are then directed around an inner radius ofthe tumor.

Combined with rotation of the subject about a vertical axis, amulti-field illumination process is used where a not yet irradiatedportion of the tumor is preferably irradiated at the further distance ofthe tumor from the proton entry point into the body. This yields thegreatest percentage of the proton delivery, as defined by the Braggpeak, into the tumor and minimizes damage to peripheral healthy tissue.

Proton Beam Therapy Synchronization with Breathing

In another embodiment, delivery of a proton beam dosage is synchronizedwith a breathing pattern of a subject. When a subject, also referred toherein as a patient, is breathing many portions of the body move witheach breath. For example, when a subject breathes the lungs move as dorelative positions of organs within the body, such as the stomach,kidneys, liver, chest muscles, skin, heart, and lungs. Generally, mostor all parts of the torso move with each breath. Indeed, the inventorshave recognized that in addition to motion of the torso with eachbreath, various motion also exists in the head and limbs with eachbreath. Motion is to be considered in delivery of a proton dose to thebody as the protons are preferentially delivered to the tumor and not tosurrounding tissue. Motion thus results in an ambiguity in where thetumor resides relative to the beam path. To partially overcome thisconcern, protons are preferentially delivered at the same point in abreathing cycle.

Initially a rhythmic pattern of breathing of a subject is determined.The cycle is observed or measured. For example, a proton beam operatorcan observe when a subject is breathing or is between breaths and cantime the delivery of the protons to a given period of each breath.Alternatively, the subject is told to inhale, exhale, and/or hold theirbreath and the protons are delivered during the commanded time period.Preferably, one or more sensors are used to determine the breathingcycle of the individual. For example, a breath monitoring sensor sensesair flow by or through the mouth or nose. Another optional sensor is achest motion sensor attached or affixed to a torso of the subject.

Once the rhythmic pattern of the subject's breathing is determined, asignal is optionally delivered to the subject to more precisely controlthe breathing frequency. For example, a display screen is placed infront of the subject directing the subject when to hold their breath andwhen to breath. Typically, a breathing control module uses input fromone or more of the breathing sensors. For example, the input is used todetermine when the next breath exhale is to complete. At the bottom ofthe breath, the control module displays a hold breath signal to thesubject, such as on a monitor, via an oral signal, digitized andautomatically generated voice command, or via a visual control signal.Preferably, a display monitor is positioned in front of the subject andthe display monitor displays at least breathing commands to the subject.Typically, the subject is directed to hold their breath for a shortperiod of time, such as about one-half, one, two, or three seconds. Theperiod of time the subject is asked to hold their breath is less thanabout ten seconds as the period of time the breath is held issynchronized to the delivery time of the proton beam to the tumor, whichis about one-half, one, two, or three seconds. While delivery of theprotons at the bottom of the breath is preferred, protons are optionallydelivered at any point in the breathing cycle, such as upon fullinhalation. Delivery at the top of the breath or when the patient isdirected to inhale deeply and hold their breath by the breathing controlmodule is optionally performed as at the top of the breath the chestcavity is largest and for some tumors the distance between the tumor andsurrounding tissue is maximized or the surrounding tissue is rarefied asa result of the increased volume. Hence, protons hitting surroundingtissue is minimized. Optionally, the display screen tells the subjectwhen they are about to be asked to hold their breath, such as with a 3,2, 1, second countdown so that the subject is aware of the task they areabout to be asked to perform.

A proton delivery control algorithm is used to synchronize delivery ofthe protons to the tumor within a given period of each breath, such asat the bottom of a breath when the subject is holding their breath. Theproton delivery control algorithm is preferably integrated with thebreathing control module. Thus, the proton delivery control algorithmknows when the subject is breathing, where in the breath cycle thesubject is, and/or when the subject is holding their breath. The protondelivery control algorithm controls when protons are injected and/orinflected into the synchrotron, when an RF signal is applied to inducean oscillation, as described supra, and when a DC voltage is applied toextract protons from the synchrotron, as described supra. Typically, theproton delivery control algorithm initiates proton inflection andsubsequent RF induced oscillation before the subject is directed to holdtheir breath or before the identified period of the breathing cycleselected for a proton delivery time. In this manner, the proton deliverycontrol algorithm can deliver protons at a selected period of thebreathing cycle by simultaneously or near simultaneously delivering thehigh DC voltage to the second pair of plates, described supra, thatresults in extraction of the protons from the synchrotron and subsequentdelivery to the subject at the selected time point. Since the period ofacceleration of protons in the synchrotron is constant, the protondelivery control algorithm is used to set an AC RF signal that matchesthe breathing cycle or directed breathing cycle of the subject.

Multi-Field Illumination

The 3-dimensional scanning system of the proton spot focal point,described supra, is preferably combined with a rotation/raster method.The method includes layer wise tumor irradiation from many directions.During a given irradiation slice, the proton beam energy is continuouslychanged according to the tissue's density in front of the tumor toresult in the beam stopping point, defined by the Bragg peak, to alwaysbe inside the tumor and inside the irradiated slice. The novel methodallows for irradiation from many directions, referred to herein asmulti-field irradiation, to achieve the maximal effective dose at thetumor level while simultaneously significantly reducing possibleside-effects on the surrounding healthy tissues in comparison withexisting methods. Essentially, the multi-field irradiation systemdistributes dose-distribution at tissue depths not yet reaching thetumor.

Although the invention has been described herein with reference tocertain preferred embodiments, one skilled in the art will readilyappreciate that other applications may be substituted for those setforth herein without departing from the spirit and scope of the presentinvention. Accordingly, the invention should only be limited by theClaims included below.

1. An apparatus for controlling intensity of charged particles extractedfrom a circulating charged particle beam path in a synchrotron, saidapparatus comprising: a radio-frequency field generator, wherein duringuse said radio-frequency generator applies a radio-frequency field tothe circulating charged particles yielding betatron oscillating chargedparticles; an extraction material, wherein at least a portion of thebetatron oscillating charged particles pass through said extractionmaterial resulting in a secondary emission electron flow; an intensitysensor, said intensity sensor determining a measure of said electronflow; and a feedback control loop comprising an intensity controller,wherein said intensity controller provides said measure of electron flowas a feedback to said radio-frequency generator, wherein said feedbackcontrol loop controls intensity of charged particles extracted from saidsynchrotron via control of said radio-frequency generator, whereinintensity comprises a number of the charged particles extracted as afunction of time.
 2. The apparatus of claim 1, further comprising: atarget signal, wherein said intensity controller calculates a differencebetween said measure of said electron flow and said target signal,wherein said intensity controller alters amplitude of saidradio-frequency field based upon said difference.
 3. The apparatus ofclaim 1, wherein said extraction material consists essentially of atomshaving six or fewer protons.
 4. The apparatus of claim 1, wherein saidextraction material comprises a foil of about thirty to one hundredmicrometers thickness, said foil comprising any of: beryllium; lithiumhydride; and carbon.
 5. The apparatus of claim 1, further comprising: atleast a one kilovolt direct current field applied across a pair ofextraction blades; and a deflector, wherein said at least a portion ofthe betatron oscillating charged particles passing through saidextraction material yield reduced energy charged particles, wherein thereduced energy charged particles pass between said pair of extractionblades, and wherein said direct current field redirects the reducedenergy charged particles through said deflector yielding intensitycontrolled extracted charged particles.
 6. The apparatus of claim 1,further comprising at least one turning magnet, wherein said turningmagnet comprises a magnetic field concentrating first magnet, whereinsaid first magnet comprises: a gap circumferentially encompassing thecirculating charged particle beam path; a first cross-section diameternot in contact with said gap; and a second cross-sectional diameterproximate said gap, wherein said second cross-section diameter is lessthan seventy percent of said first cross-sectional diameter, wherein amagnetic field passing through said first cross-sectional diameterconcentrates in said second cross-sectional diameter before crossingsaid gap.
 7. A method for controlling intensity of charged particlesextracted from a circulating charged particle beam path in asynchrotron, said method comprising the steps of: generating aradio-frequency field using a radio-frequency field generator, whereinsaid radio-frequency generator applies the radio-frequency field acrossthe circulating charged particle beam path yielding oscillating chargedparticles; traversing at least a portion of the oscillating chargedparticles through an extraction material yielding a secondary emissionelectron flow; determining a measure of the electron flow using anintensity sensor; and providing the measure of the electron flow to anintensity controller via a feedback control loop, wherein said intensitycontroller controls intensity of charged particles extracted from saidsynchrotron via control of said radio-frequency generator, whereinintensity comprises a number of the charged particles extracted as afunction of time.
 8. The method of claim 7, further comprising the stepof: determining a difference between a target signal and said measure ofelectron flow, wherein said intensity controller alters amplitude ofsaid radio-frequency field based upon said difference.
 9. An apparatusfor extracting intensity controlled charged particles from chargedparticles circulating in a synchrotron of a charged particle cancertherapy system, comprising: oscillation blades, said oscillation bladescomprising a radio-frequency voltage across said blades during use, saidradio-frequency inducing oscillating charged particles from the chargedparticles circulating in said synchrotron; an extraction material insaid synchrotron, wherein the oscillating charged particles traversesaid extraction material during use generating both reduced energycharged particles and secondary emission electrons; and extractionblades, said extraction blades extracting said reduced energy chargedparticles from said synchrotron.
 10. The apparatus of claim 9, furthercomprising: a feedback intensity controller, wherein said intensitycontroller generates a measure of the secondary emission electrons,wherein said intensity controller generates a comparison of said measureand a target signal, wherein said intensity controller adjusts amplitudeof said radio-frequency voltage based on said comparison.
 11. Theapparatus of claim 10, wherein said extraction blades comprises anextraction field across said extraction blades, wherein the reducedenergy charged particles, comprises movement along a radius of curvaturepassing through said extraction blades, wherein the reduced energycharge particles extract from said synchrotron after passing throughsaid extraction field.
 12. The apparatus of claim 9, further comprisinga main controller, said main controller controlling: acceleration of thecirculating charged particles to a target energy level; and intensity ofsaid radio-frequency voltage yielding a target intensity level of theextracted charged particles.
 13. A method for extracting intensitycontrolled charged particles from charged particles circulating in asynchrotron, comprising the steps of: inducing oscillating chargedparticles from the charged particles circulating in said synchrotronusing a radio-frequency voltage applied across a pair of oscillationblades, traversing the oscillating charged particles through anextraction material in said synchrotron, said step of traversinggenerating both reduced energy charged particles and a current; andextracting said reduced energy charged particles from said synchrotronby passing the reduced energy charged particles through an extractionfield between two extraction blades.
 14. The method of claim 13, furthercomprising the steps of: generating a measure of the current; generatinga comparison of said measure and a target signal using an intensitycontroller; and adjusting amplitude of said radio-frequency voltagebased on said comparison.
 15. The method of claim 14, wherein thereduced energy charged particles, comprises movement along a radius ofcurvature passing through said extraction blades, wherein the reducedenergy charge particles extract from said synchrotron after passingthrough said extraction field.
 16. The method of claim 13, furthercomprising the step of: controlling acceleration of the circulatingcharged particles to a target energy level of the extracted chargedparticles; and controlling intensity of said radio-frequency voltageyielding a target intensity level of the extracted charged particles.17. A method for extracting a circulating charged particle beam from asynchrotron, comprising the steps of: transmitting the circulatingcharged particle beam through an extraction material, said extractionmaterial yielding both: a reduced energy charged particle beam; and asecondary emission current; applying a field of at least five hundredvolts across a pair of extraction blades; passing the reduced energycharged particle beam between said pair of extraction blades, whereinsaid field redirects the reduced energy charged particle as an extractedcharged particle beam.
 18. The method of claim 17, further comprisingthe step of: controlling intensity of the energy controlled extractedcharged beam with an intensity controller.
 19. The method of claim 18,wherein said step of controlling comprises the steps of: inputting afeedback signal to said intensity controller, said secondary emissioncurrent converted to said feedback signal; comparing said feedbacksignal to an irradiation plan intensity; adjusting betatron oscillationwith said intensity controller until said feedback signal proximatelyequals said irradiation plan intensity.